If you import then export from Picasa, you will lose image quality. The amount of loss that is acceptable is not something that we can determine for you - that is a personal decision. For me, I would keep the originals before they ever were imported into Picasa - so I have the full resolution original to archive forever.
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dpollittFeb 26 '13 at 3:11

I'm with @dpollitt - for the amount any of us have spent on camera & kit it makes no sense to destroy 'originals' in favour of poorer quality copies. Storage is so cheap that it's really not an issue.
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James SnellApr 3 '13 at 10:52

It might be worth considering that in some parts of the world $50 are a significant investment and perhaps the question stems from there – hardware might be difficult to come by or too expensive for a casual purchase, relative to income. (Though that aside I'd vote for "original, if possible" as well.)
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CorneliusJul 7 '14 at 8:35

4 Answers
4

Don't shrink them. In the grand scheme of things, you're talking about a very small amount of storage — your collection of 8000 photos at 6 megabytes fits in under 50 gigabytes. Even with high-quality archival storage, this isn't very much.

Spend a small amount of money and get a larger drive and set up a back-up solution.

To put it another way: the only optimal answer is the unedited originals as they are right now.

Make sure the number of pixels for the width and height are both multiples of 8 (1024x768 is fine, 1020x765 isn't). Otherwise the image quality will be significantly worse (jaggies etc. will be more obvious), especially at lower JPEG compression rate.

In other words, if you stick to the "multiples of 8" rule, you can reduce the compression rate further, making the file size even smaller.

Could you elaborate on why multiple of 8 is good?
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Håkon K. OlafsenMar 1 '13 at 11:28

Because JPEG internally chucks the picture into 8x8 pixel images and then runs the compression on that. (Although I don't know if that multiples of 8 rule actually works.)
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UnapiedraMar 1 '13 at 11:43

The resolution of photographs you post online to Picasa depends on why you want to do that. Do you share photographs with friends, let everyone download a portion of common pics or want to use it as a backup?

I do not use Picasa, but I use Panoramio, also by Google. When I upload photos that I know I will reference in my blog, I use 900x600 resolution, because this is the one which suits my blog's design the best. It also looks good when viewed on Google Maps.

The decision also depends on the circulation breadth of your photographs. If you want people to use them as wallpapers (even without your consent) or print them out or use in some third-party application like private invitations or pocket calendars, then a typical HD-screen resolution would suit you fine. I do not enjoy the thought of losing track of my photos on the Internet, that is why I prefer to scale them down to 900x600 px. This is a good resolution for viewing images on most standard laptops, and it will look no good if printed out.

Another possibility, as D3C4FF mentioned, is that you plan to use Picasa as a back-up storage. In this case, then upload photographs in the highest resolution possible. I do not know about you, but personally I do not trust online storage resources as much as I believe in the power of hard drives. If you want to back-up your photo collection online, you might consider creating an offline storage for that.

UPDATE:
Forgot to comment on the question of image quality. I do not know what other options are available besides "automatic", but in Photoshop JPEG quality level 9, in Lightroom quality 80% are usually more than enough.

You have to ask yourself why you want to upload the photos online.
If its for backup and archiving (to save space on your harddrive), then your best bet would be to upload it at the maximum possible quality.

If you just want to share your photos among family and friends, then re-sizing it to something around the 1920x1080 (generic wallpaper size) is probably good enough (most people's screens aren't higher res than that). 1024*768 is a bit on the small size (the max for the tinypic site).

Aside for easy viewing and saving space, the only reason i'd reduce image size is to make it quicker to upload images if you are on a slow internet connection. If you connection is relatively fast then its not a worry.

Check out this thread about backing up photos if its relevant to you. I'd personally say that harddrives (500GB plus) only set you back about $50 these days so it might be worth while investing in one of these if you aren't shooting full time.